For now I have tried different ways to get the phone running back:
1) * I have successfully flashed LT15i 4.0.2.A.0.42 Generic Global World rom
* Rebooted, but it could not read the sim card. (all other features, such as wifi, works great)
* Then I connected phone to PC Companion, and upgraded to ICS.
* Rebooted, but again it could not read sim again.
2) * Then I have flashed LT15i 4.1.B.0.431 Generic Global World, rebooted, again it could not read sim card.
* After that I connected phone to Software Updater, re-installed system from there, rebooted, again it did not read sim card.
While trying all these methods, I could not connect phone with fastboot option (connecting phone while pressing menu button). If I could boot phone with fastboot, at least I could try to install custom kernel & rom.
Anybody has any ideas what can I do to get my phone back :/